Fibers balers are necessary for the reason that all types of fibers exhibit very low apparent densities unless they are compacted and constrained. This compaction allows more efficient storage and shipping of the fiber, since the compacted form of the fiber takes up less volume, requires less warehouse space, and fewer containers or vehicles to transport. Other materials besides fiber also exist naturally in a low density form and share in the need for compaction and constraint for the same reasons as fiber. Such materials include paper, cardboard, wood shavings, refuse and metal shavings, just to name a few. The art of baling is well known and many different types of balers exist today. These balers all share some common features. They have one or more compaction boxes for the material to be baled, a hydraulic ram to provide the compaction energy, and a platen to provide the uniform pressure across the entire cross section of the bale. Additionally, they provide some means for allowing bands, straps or wires to be employed and secured around the bales after the material has been sufficiently compacted, but before the pressure is released from the bale.
Using existing art, if the baler has only one compaction box and no precompaction device, the output of the baler is relatively low. The reason for this is that the platen is connected to a hydraulic ram, and the rate at which the hydraulic ram can move is proportional to the volumetric output of the hydraulic pump which powers the ram. The primary purpose of this hydraulic pump is, of course, to provide high pressure to move the platen just far enough during the final compaction cycle that the bale is compacted to the desired density. In single compaction box with no precompaction equipment though, a secondary purpose of this hydraulic pump is to provide the energy and pressure necessary to accomplish, in several steps, precompaction of successive charges of fiber or material to an intermediate density allowing the box to be filled before the final compaction occurs. Each one of these compaction steps is slow because the ram moves only at a rate determined by the volumetric capacity of the hydraulic pump. Not only is each of the compaction steps slow, but the retraction of the ram is slow as well, because it too, is determined by the volumetric capacity of the hydraulic pump. Single box balers without trampers usually, but not always, have the compression box in a horizontal orientation.
To increase the output associated with a single hydraulic system, and associated single ram, single platen, and single compaction box, the known art of baling has come to include a variety of different types of precompaction devices. These precompaction devices, often known as trampers, are typically used on fiber and consist of metal boxes with some type of tramper foot. Because of the much greater volume of material handled, the tramping step is usually more time consuming, per pound of material handed, than the final compaction step, so several precompacting devices are often used to feed multiple high pressure boxes. Once loaded, however, the boxes are moved under a single platen and hydraulic ram for the final compaction step. In this manner, the most costly components of the baler are kept in more continuous use, and are therefore used to better effect.
U.S. Pat. No. 4,936,206 to Miles et al discloses a compacting apparatus having a compression chamber defined by side plates and first and second movable end platens, a long stroke small diameter hydraulic piston pushes the first end platen against a charge toward the second end plate, partially compressing the charge. The first end platen is then latched in a fixed position while the second end platen by the short-stroke large diameter hydraulic piston applies a further compressive stroke. The fully compressed charge is pushed out of the compression chamber bound loosely while fully compressed.
U.S. Pat. No. 3,451,190 to Tezuka discloses a device having four hydraulic cylinders for compacting trash and garbage to remove liquid. There are additional cylinders for actuation of gates and wrapping equipment.
U.S. Pat. Nos. 3,384,007; 3,621,775; 4,953,458 and 5,325,770 are typical of prior art compaction devices. However, none of the patents show the use of primary and a secondary hydraulic cylinders to move a platen to accomplish both tramping and final compaction.